Forced air system air filter

Abstract

An HVAC filter having a pleated paper filter and a plastic pre-filter, the filter and pre-filter are mounted in a parallel relation in the frame. The plastic pre-filter includes a plastic mesh having a plurality of openings, and an irregular surface on the inlet side to prevent matting of filtered material.

What is claimed is: 
     
       1. An air filter comprising: a frame;   a pleated filter element supported by the frame; and   a substantially planar pre-filter formed from woven plastic strands and supported by the frame in a side-by-side relationship with the pleated filter to filter air which passes through the pleated filter.   
     
     
       2. The filter of claim 1, wherein the pleated filter is formed from paper. 
     
     
       3. The filter of claim 2, wherein the paper includes fiberglass fibers. 
     
     
       4. The filter of claim 1, wherein the plastic strands have different diameters and are woven such that the pre-filter has an irregular surface. 
     
     
       5. The filter of claim 4, wherein the plastic strands are polypropylene. 
     
     
       6. The filter of claim 1, wherein the frame is rectangular, and is fabricated from elongated sections having a generally U-shaped cross-section. 
     
     
       7. The filter of claim 1, wherein the frame is rectangular, and is fabricated from elongated sections having a generally U-shaped cross-section. 
     
     
       8. An air filter comprising: a frame;   a pleated filter element supported by the frame; and   a substantially planar woven, plastic mesh supported by the frame in a side-by-side relationship with the pleated filter to filter air which passes through the pleated filter.   
     
     
       9. The filter of claim 8, wherein the pleated filter is formed from paper. 
     
     
       10. The filter of claim 9, wherein the paper includes fiberglass fibers. 
     
     
       11. The filter of claim 9, wherein plastic mesh includes plastic strands having different diameters and are woven such that the plastic mesh has an irregular surface. 
     
     
       12. The filter of claim 11, wherein the plastic strands are polypropylene. 
     
     
       13. The filter of claim 9, wherein the frame is rectangular, and is fabricated from elongated sections having a generally U-shaped cross-section. 
     
     
       14. An air handling unit defining a path of airflow, the unit comprising: a filter support; and   a filter assembly supported by the support within the path of airflow through the air handling unit, the filter assembly comprising; a frame;   a pleated filter element supported by the frame, and.   a substantially planar plastic pre-filter formed from woven plastic strands and supported by the frame in a side-by-side relationship with the pleated filter to filter air which passes through the pleated filter.     
     
     
       15. The filter of claim 14, wherein the pleated filter is formed from paper. 
     
     
       16. The filter of claim 14, wherein the plastic strands have different diameters and are woven such that the pre-filter has an irregular surface. 
     
     
       17. An air filter comprising: a frame;   a pleated filter element supported by the frame; and   a plastic pre-filter formed from plastic strands supported by the frame in a side-by-side relationship with the pleated filter to filter air which passes through the pleated filter, wherein the plastic strands have different diameters such that the pre-filter has an irregular surface.   
     
     
       18. The filter of claim 17 wherein the plastic strands are polypropylene. 
     
     
       19. The filter of claim 17 wherein the plastic strands are woven.